Centrifugal blower



Feb. 11, 1941. A EVANS 2,231,062

CENTRIFUGAL BLOWER Filed Jan. 7, 1939 INVENTOR ADDISON W. EVANS ATTORNEYPatented Feb. 11, 1941 CENTRIFUGAL BLOWER Addison W. Evans, Torrington,Conn, assignor to The Torrington Manufacturing 00., Torrington, Conn, acorporation of Connecticut Application January 7, 1939, Serial No.249,714

10 Claims.

This invention relates to improvements in centrifugal blowers, andparticularly to an improved rotor, fan or blower wheel assembly,together with improvements in methods ofmaking same.

Centrifugal blower wheels have usually heretofore been constructed of aplurality of separate vane or blade-forming elements, each provided atits ends with a flange or the like through which the blades are riveted,welded or other- 10 wise secured to the shaft mounting elements, which,if at the end of the wheel, are often known as end rings. The principalprevailing objection to this form of blade is found in that the laborand the equipment required for the separate securement of the individualblades of a rotor of this type to the shaft mounting elements, entail asubstantial expense.

Several attempts have heretofore been made in the art to form blowerwheels or rotors by constructing the rim or body of the wheel of asingle continuous strip of sheet metal or the like, this strip beingpunched or slitted longitudinally, i. e., in the direction of the axisof the Wheel, and the metal between the slits being formed and shaped toprovide the blades. It is to this type of construction that the presentinvention pertains, and in the improvement of which is found itsprincipal objective. As is understood, the blower wheels of the typelast referred to, and which have heretofore appeared in the art, werecharacterized by a high proportion of metal spoilage and rejects becauseof the tendency, when forming up the individual blades, and under stressor operation, for the lines of fracture therebetween and defining theblades to extend endwise therebeyond. This difliculty may be partlyovercome by using metal of heavier gauge, but thus entailing addedexpense and needlessly increasing the weight of the wheel. The presentinvention has 40 as a further important object, an avoidance of thedifiiculty last above discussed, without increasing the Weight of thewheel.

Still other objects of the invention include an improved manner ofsecurement of the shaft mounting elements to a blower body of sheetmetal type, so as to obviate or minimize the number of rivets or theextent of welding or the like, usually resorted to for the assemblysecurement of these parts.

Yet another object of the invention is attained in an arrangementenabling the use of sheet metal of a lighter gauge in the constructionof blower wheels of substantial length, this expedient consisting, inthe disclosed example, of an intermediate external tension elementembracing the blades, and so located as to resist deflection thereofunder the influenec of centrifugal stresses.

The foregoing and numerous other objects will appear from the followingdetailed description, 5 considered in connection with the accompanyingdrawing, in which:

Fig. 1 is an isometric view showing a blower wheel constructed inaccordance with the present invention; Fig. 2 is an enlarged fragmentaryplan view of a peripheral end portion of the blower shown by Fig. 1;Fig. 3 is an enlarged fragmentary showing of a plurality of the bladesand tension element, as viewed over a small area centrally of the outersurface of the rotor or wheel; Fig. 4 is a section along the planeindicated by line. l--l of Fig. 3; Fig. 5 is a fragmentary end view of aperipheral portion of the rotor showing certain details of construction,and

Fig. 6 is a section of a portion of the end ring and adjacent body orrim structure, as viewed along line 6-6 of Fig. 5.

Referring now by characters of reference to the drawing, and first toFig. 1, the assembly shown by way of example is a double inlet blowerwheel of reasonably large diameter, the inlets to which are at the ends.The blower shown is not provided with a center plate or otherintermediate shaft mounting element, although obviously such an elementmay be utilized when desired, for certain types of service.

The shaft mounting elements or end rings are indicated at It) and II,and each of these consists preferably of a one-piece punched annulus ofsheet metal characterized by radial arms or spokes l2, of which threeare shown, serving to connect the peripheral portion l3, to the centraldisk or spider portion [4, the latter being optionally provided withopenings l5 for the reception of stud bolts, cap screws or other holdingelements engaging a shaft collar (not shown). The rigidity of the spokesI2 is considerably augmented by pressed-in ribs or the like I 6. Theoriginal diameter of each of the formed end rings, is somewhat greaterthan the intended finished diameter of the wheel, and to this end theannu lar peripheral flange l3 of each end ring extends somewhat beyondthe periphery of the rim as it appears in Fig. 1; this extra material atthe margin of the ring is resorted to as an assembly expedient, bycrimping to the rim or body of the wheel, as is hereinafter more fullypointed out.

Referring now more particularly to the rim or body of the wheel, it isa. preference. that, for lightness and reduction of cost of assembly inproduction, this element be formed of a single strip of sheet metal,although obviously more than one may be employed if desired. This strip,shown in finished form by Figs. 1, 2 and 3 particularly, is eitheroriginally supplied with, or is cut to provide substantially evenparallel margins thereon so that the strip is of fairly uniform widththroughout its length, and in case as is preferred, a single element beused to form the periphery of the blower wheel, this length is of coursethe same as or somewhat greater than the circumference of the finishedwheel.

Considering in a preferred order the steps involved in the method offorming up the body, the strip indicated generally at 20 in its finishedform, is subjected to a first operation of gauging and perforatingsomewhat inwardly of the opposite lateral margins of the strip, aplurality of evenly spaced rounded apertures 2|. In the case of a doubleinlet wheel of the type disclosed, in which each end is provided with amounting ring or the like, as well as in a single inlet wheel, theopposite margins of the strip 20 will be perforated at correspondingpoints so as to provide a double row of the openings 2| in such mannerthat the openings are in pairs opposite each other on a line at adistinct angle, in many cases a right angle to the margins or length ofthe strip. The openings 2| may be produced easily and at a low cost byknown and available punch press or other known equipment, which need nothere be described in detail since it constitutes of itself no part ofthe present invention.

The ensuing step in forming the body strip consists in slitting,punching ofotherwise cutting the strip along a series of evenly spacedparallel lines connecting the openings 2| above described. It is apreference that, as the strip is so apertured these lines, althoughstraight for the greater part of their length, be curved somewhat attheir ends, as best appears. in Fig. 2, these curved portions of theadjacent blade lines being indicated respectively at 23 and 24.

Either simultaneously with the slitting or punching operation orfollowing it, the portions intervening the transverse slits, therectilinear.

parts of which are indicated at 25 in the finished body, are bent out ofthe plane of the strip, each to the same extent and shape, so as toprovide the requisite blade form and angle.

Another operation which, as will be understood, may be conductedconcurrently with either or both of those aforesaid, consists in bendingup a marginal portion of the strip 20 so as to form thereon one or moreflanges 26 (Fig. 6), each such flange being preferably at a right angleto the body of the strip and in assembly being disposed radially,preferably .outwardly, of theflnished rotor body. A still furtheroperation which may be conducted concurrently with or subsequently toany of those aforesaid, consists in providing by any suitable or knownequipment, a plurality of substantially evenly spaced and radiallyextending notches 21, these recesses extending inwardly to a slightextent from the outermost periphery of the flange 26. The strip fromwhich the body is formed, may be now considered ready for assembly tothe end ring or rings, being now pierced between blades, with the bladesshaped, the peripheral flange or flanges 26 formed thereon, and they inturn being peripherally notched to facilitate assumption by the body ofthe required cylindrical form.

The circumferential blade strip is now passed through a suitable shapingagency, for example, a roll coiler, to bring it to the desiredcylindrical form, the radius of curvature to be imparted as by the rollcoiler, being determined by the length of strip, and more particularlyby the diameter of completed wheel orrotor. Incident to the calleroperation on the body-forming strip, there is applied thereto,preferably midway between the ends of the blades 30, a tension band orthe like which is of a length approximating the circumference of thefinished wheel. A suitable form of this element is indicated at 3| asconsisting of a wire of round section, preferably of a metal conformingsomewhat to that of the body of the rotor, for example, a drawn steelwire. It will be understood that the application of the band 3| at thetime of coiling the body strip, results in its serving a distinctpurpose in the method outlined, in that the band prevents any tendencyof the strip throughout subsequent steps, to reassume its rectilinearform. As will hereinafter appear, the band or wire 3i further serves animportant structural purpose in the finished assembly, as a restrainingor confining element, being essentially a tension member. The ends ofthe wire are welded together to form a smooth joint, being preferablybutt welded as at 32 so as to obviate any substantial overlap.

It is a preference, incident to forming the slits 25 as by punching inorder to define the blades of the wheel, that alternate slits 25 in thestrip 20 be provided with notches or depressions best shown at 33 (Fig.3), the resulting recesses serving as seats for the tension band or wire3|, and conforming substantially thereto in curvature or other shaping.This arrangement serves as will appear, to enable locating the band orwire 3| substantially within the peripheral confines of the body proper,and the interfitting relation of the tension band 3| and the blades,serves in operation or handling of the fan, to obviate any tendency ofthe band to slip in either direction axially of the rotor or otherwiseto become displaced. If desired, the band 3| may be even more rigidlypositioned by spot welding it to some or all of the blades, as indicatedat 3IA (Fig. 3).

It is preferred that the length of the strip 20 be such that its endswill meet smoothly, without overlap, and the strip ends weldedinternally to the and ring or rings. However, if desired, the bladedpor'tion of the strip 20 may be provided with an extension beyond one orboth of the terminal blades of .the strip, and when coiled intocylindrical form, the extended areas are.

overlapped between the end blades of the strip, and lap weldedinternally of the rotor body, for example along a zone or line asindicated at 3| (Fig. 1).

There now remains to be described, the assembly of the finishedcylindrical body rim to the one or more shaft-mounting rings which may,for example, consist of the end rings constituted by elements l2, l3,l4, etc. The assembly of the rings and body consists, through suitablejigs or holding agencies, in locating the ring portions of the rim l3including portions 35 and 36, are folded over the flange 26 m that thepart 35 overlies the flange, the part 36 then being doubled over thefinished rim l3 and brought parallel thereto with the efiect of firmlygripping or embracing the flange 26 between the elements l3 and 36.

It may be noted that the end ring (2, for example, is initially or laterso formed as to pro- 'vlde an offset 31 resulting in a. shoulder 40constituting a seat or rest for the margin of the strip or rim. It is afurther preference that the original diameter of the ring l2 be suchthat, having regard for the gauge of the body and hence the flange 26,when the portions 35 and 36 are crimped into assembly as shown by Fig.6, the end margin of the downturned flange 36 abuts the portion of thestrip 20 just inwardly of the flange. The ofiset 31 also offers theadvantage of providing a seat for the reception, between the ring andedge of strip ill, of welding metal as indicated at H. A line of weldingin this zone may not be necessary in the smaller sizes of wheels, butwhen desired for strengthening in the larger sizes, may be utilized assuggested by Fig, 6.

It is a preference, as before noted, that the line of openings 2!,defining the ends of the blades, be located somewhat inwardly of themargin of the strip forming the bladed portion of the body, so that inthe finished rotor or wheel, there remains at each end an appreciablecylindrical portion 42. This arrangement tends to obviate any likelihoodof fracture of the metal beyond the openings 2|, incident to anyvibration of the finished wheel, or due to stresses in forming up thebladed strip.

It is to be noted that in the assembly described, there is a distinctcoaction and cooperative relation between the crimped end-ring assemblyand the intermediate tension ring, with the stripformed body, in thateach of the holding and assembly expedients provides a continuous zoneof securement, in distinction from the spaced points of anchorageprovided by the more usual riveted construction. The presently describedarrangement enables the use of a. lighter gauge of metal, or converselystated, produces a. more rigid wheel, utilizing any given gauge ofmetal. The characteristic of rigidity'is an important feature, since therotor of the disclosed example cannot, without resulting in adverse airefiects, be internally braced after the manner of many stationarycylindrical structures.

Although the example disclosed has been described throughout as a weldedstructure, it is to be noted that soldering, brazing, or in some casesriveting may be employed within the scope of some of the aspects of theinvention, and that a number of changes may be made in the severalelements and their assembly as well as in the steps involved in thedescribed method of producing the article, all without departing fromthe full intended scope and spirit of the invention as defined by theclaims hereunto appended.

I claim:

1. A rotor for a centrifugal blower, including a rim or body formed of acontinuous strip of sheet metal provided with slits and formed betweenthe slits to provide a. plurality of blades, and provided with acontinuous margin adjacent the ends of the blades, said marginal portionbeing bent radially beyond the cylindrical plane of the adjacent strip,and provided with a plurality of radially extending notches, and ashaftmounting ring of sheet metal including a periphcral portion foldedinto crimped assembled relation to the rim or body and embracing andcovering the notched areas of said marginal portion.

2. An open end centrifugal blower wheel or fan, including a one-piecebladed body or rim provided with a notched, radially extending flangelying substantially in the plane of the end of the wheel, a one-pieceend ring of sheet metal having a rim portion of greater diameter thanthat of the body of the wheel, and a doubled portion on the rim of thering, which engages opposite sides of said flange and overlies thenotched portion thereof for securement oi the end ring to the body ofthe wheel.

3. A centrifugal blower wheel of double end type, including a body orrim element of cylindrical form, constructed of a strip of sheet metalcharacterized by slits of axial trend and provided with roundedapertures at the ends of the slits, and inwardly of the lateral marginsof the strip, the metal portions intervening the slits and aperturesbeing shaped and bent inwardly of the cylindrical plane of the body toform blades of the desired form and angle, a radially extending flangeformed on each of the body beyond the blade-forming portions thereof,the flanges being radially and peripherally slotted, a shaft mountingring at each end of the body, each such ring including an annular offsetproviding a shoulder or seat for the body strip, a peripheral portionoutwardly of the shoulder, folded and crimped into embracing engagementwith the flange and overlying the notched portion thereof for assemblyof the ring to the body, a tension band embracing the body on a bladedportion thereof substantially between the shaft mounting rings, aplurality of the blades being provided with recesses conforming to andpartially embracing the tension band and enacting therewith to preventaxial displacement of the band along the blades.

4. In a rotor for a centrifugal blower, a rotor rim or body formed of astrip of sheet metal curved to cylindrical form, and provided withincisions of a generally axial trend, the metal between which is shapedand inclined to form, a plurality of blades, at least one margin of theblade or body being provided with an out-turned radial flange, theflange being provided with a plurality of indents or interrupted areasextending depthwise of the flange substantially throughout its fullwidth or depth, and an end ring formed of sheet metal and having aperipheral portion bent over said flange in embracing relation theretofor the purpose of covering said indents, embracing the flange andserving to secure the end ring to the rim or body of the rotor.

5. A centrifugal blower wheel of double end type, including a body orrim element of cylindrical form, constructed of a strip of sheet metalcharacterized by slits of axial trend and provided with roimdedapertures at the ends of the slits, and inwardly of the lateral marginsof the strip, the metal portions intervening the slits and providing ashoulder or seat for the body strip,

a peripheral portion outwardly of the shoulder.

'folded and crimped into embracing engagement with the flange andoverlying the notched portion thereof for assembly of the ring to thebody.

6. A centrifugal blower wheel of double open end type, including a bodyelement of cylindrical form, constructed of a. strip of sheet metalcharacterized by slits of axial trend terminating inwardly of thelateral margins of the strip, the

metal portions intervening the slits being shaped and bent inwardly ofthe cylindrical plane of the body to form blades of the desired form andangle, a' radially extending flange formed on each of the body marginsbeyond the bladeforming portions thereof, the flanges being radiallyslotted, a shaft mounting ring at each end of the body, each said ringincluding antannular oifset providing a shoulder or seat for the bodystrip, and a peripheral portion outwardly of the shoulder, secured inengagement with the flange and overlying the notched portions thereof.

7. A centrifugal blower wheel of double open end type including a bodyor rim element of cylindrical form, constructed of a single strip ofsheet metal characterized by slots of axial trend terminating inwardlyof the lateral margins of the strip, the portions intervening the slitsbeing shaped and bent inwardly of the cylindrical plane of the body toform blades of the desired form and angle, an out-turned radiallyextending flange formed on each of the opposite margins of the bodybeyond the blade-forming portions thereof, the flanges being indented orinterrupted substantially over their full width, and radially ordepthwise thereof, a shaft mounting ring at each end of the body, eachsuch ring being formed to provide an annular offset constituting ashoulder or seat for the body strip and extended outwardly of the stripand into embracing engagement with the flange so as to overlie and gripthe interrupted or indented portions of the flange for holding the ringin assembly with 1 the body.

8. An open end centrifugal blower wheel or fan, including a one-piecebody provided with blades, and including a notched, radially extendingflange lying substantially in the plane of the end of the wheel, aone-piece end ring of sheet metal having a rim portion of greaterdiameter than that of the body of the wheel, and a doubled portion onthe rim of the ring which engages opposite sides of said flange andoverlies the notched portion thereof for securement of the end ring tothe body of the wheel, one of the elements of said doubled portion lyingin a plane normal to the axis of the wheel and having an annular edgeportion snugly abutting and endwise overlying the adjacent lateralmargin of the body, in a manner directly to resist any tendency ofoutward movement of the body, under centrifugal stresses.

9. An open end centrifugal blower wheel or fan, including a one-piecebody provided with blades, and including a notched, radially extendingflange lying substantially in the plane of the end of the wheel, aone-piece end ring of sheet metal having a rim portion of greaterdiameter than that of the body of the wheel, a doubled portion on therim. of the ring, which engages opposite sides of said flange andoverlies the notched portion thereof for securement of the end ring tothe body of the wheel, one of the elements of the doubled portion on therim, lying in a plane normal to the axis of the wheel and having anannular edge portion snugly abutting and directly overlying the adjacentlateral margin of the body, in a manner directly to resist any tendencyof outward movement of the body under centrifugal stresses, and meanssecuring the body to the end ring, along a substantially continuous zoneof junction of the body and end ring, interiorly of the body.

10. A centrifugal blower wheel or fan including a one-piece body formedto provide blades thereon, and further provided with a notched radiallyextending flange lying substantially in the plane of the end of thewheel, a one-piece end ring of sheet metal having a rim portion ofgreater diameter than that of the body, the outer portion of the ringbeing bent axially outwardly to provide an annular offset constituting aseat on which the body of the wheel rests, the rim of the ring outwardlyof said seat including a doubled portion which engages opposite sides ofsaid notched flange and overlies the notched portion thereof forsecurement of the end ring to the body of the wheel, said doubledportion terminating just over, and coacting with said annular seat, toembrace the margin of the body between said doubled portion and seat.

ADDISON W. EVANS.

